Aromatic polyamide pulp by means of continuous transferable polymerization-orientation method and a process for preparation thereof

Abstract

A process for the preparation of aromatic polyamide pulp having both excellent physical properties and a high degree of polymerization by continuous polymerization and orientation by using of mixed solutions. The solutions are prepared by reacting diamine with aromatic diacid dichloride in an amide and/or urea-based polymerization solvent containing inorganic salts, or a mixture of inorganic salts and a Lewis acid compound. The process can be practiced by polymerization-orientation apparatus located on the continuous transferable polymerization-orientation means comprised of a belt and one or more stirring bars.

What is claimed is: 
     
       1. A process for the preparation of aromatic polyamide pulp, which process comprises the steps of: urea-containing solvent, or a mixture thereof, and mixing therewith 20 to 50 wt % of one or more aromatic diacid dichlorides; (c) adding said first mixture and the remainder 50 to 80 wt % of aromatic diacid dichloride to a continuous mixer simultaneously with mixing, and then ejecting said mixed solution onto a continuous transferable polymerization-orientation means;   (d) polymerizing and orienting said mixed solution obtained in (c) by polymerization orientation means located on the continuous transferable polymerization-orientation means;   (e) maintaining and maturing said polymerized and oriented mixed solution obtained in (d) in the continuous transferable polymerization-orientation means;   (f) precipitating the material obtained in (e) into a precipitating solution, and then pulverizing and drying the precipitate in pulping means;   (g) obtaining an aromatic polyamide pulp having repeating units represented by the following formula (A): ##STR9## wherein R 1 , R 2  are selected from the group consisting of the following aromatic groups, ##STR10##  X is H, Cl, Br, ##STR11##  or alkyl or alkoxy group of from 1 to 4 carbon atoms, Y is ##STR12##   
     
     
       2. An aromatic polyamide pulp having an inherent viscosity of more than 4.7 g/dl and a Canadian Standard Freeness of less than 650 ml. 
     
     
       3. The aromatic polyamide pulp according to claim 2, wherein said aromatic polyamide is poly(p-phenyleneterephthalamide). 
     
     
       4. An aromatic polyamide pulp having an inherent viscosity of more than 3.0 g/dl, a Canadian Standard Freeness of less than 650 ml and a pulp length distribution at 14 mesh or more or less than 30%, at 28 mesh or more of more than 30%, at 48 mesh or more of more than 60%, at 100 mesh or more of more than 70%, and at 150 mesh or less of less than 25%. 
     
     
       5. The aromatic polyamide pulp according to claim 4, wherein said aromatic polyamide is poly(p-phenyleneterephthalamide). 
     
     
       6. The process of claim 1, wherein said polymerization solvent further comprises one or more inorganic salts. 
     
     
       7. The process according to claim 1, wherein said organic solvents are selected from the group consisting of N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, hexamethylphosphoamide, N,N-dimethylformamide, N,N,N',N'-tetramethylurea, and mixtures thereof. 
     
     
       8. The process according to claim 6, wherein said inorganic salts are selected from the group consisting of CaCl 2 , LiCl, NaCl, KCl, LiBr, KBr, and mixtures thereof. 
     
     
       9. The process according to claim 8, wherein the amount of said inorganic salts is 0.1 to 12% by weight of said polymerization solvent. 
     
     
       10. The process according to claim 1, where one or more Lewis acid compounds is added to said polymerization solvent. 
     
     
       11. The process according to claim 10, wherein said one or more Lewis acid compounds is selected from the group consisting of BF 2 , BCl 3 , AlCl 3 , MgCl 2 , FeCl 2 , FeCl 3 , ZnCl 2 , SbCl 2 , HgCl 2 , and mixture thereof. 
     
     
       12. The process according to claim 10, wherein the amount of said one or more Lewis acid compounds is 0.5 to 5% by weight of said polymerization solvent. 
     
     
       13. The process according to claim 1, wherein said aromatic diamine/polymerization solvent solution and said 20˜50 wt % of said aromatic diacid dichloride in step (b), and said first mixture and said remainder aromatic diacid dichloride of step (c) are mixed in parallel direction. 
     
     
       14. The process according to claim 13, wherein said mixing is accomplished with the ejector. 
     
     
       15. The process according to claim 1, wherein said continuous transferable polymerization-orientation means comprises a belt and one or more stirring bars. 
     
     
       16. The process according to claim 15, wherein said one or more stirring bars rotate around an axis perpendicular to an upper surface of the belt. 
     
     
       17. The process according to claim 15, comprising plural stirring bars. 
     
     
       18. The process according to claim 15, wherein a guide is provided to prevent said solution ejected from flowing in a direction opposite to the progress of the belt. 
     
     
       19. The process according to claim 15, wherein guides are provided at both edges of said belt to prevent said solution from flowing to the side of said belt. 
     
     
       20. The process according to claim 15, wherein said one or more stirring bars are provided at an upper part of said belt. 
     
     
       21. The process according to claim 1, wherein in step (c) said solution is ejected on the continuous transferable polymerization-orientation means by free fall. 
     
     
       22. The process according to claim 1, wherein the concentration of said polymer is 3 to 15% by weight of said total polymerization solution. 
     
     
       23. The process according to claim 1, wherein polymerization and orientation is carried out until the polymer is gelled. 
     
     
       24. The process according to claim 1, wherein in step (e) polymer solution is matured by maintaining said solution at a temperature of 25° to 100° C., for 10 to 60 mins. 
     
     
       25. The process according to claim 1, wherein said precipitating solution is selected from the group consisting of water, basic aqueous solution, and mixtures of one water or a basic aqueous solution with said polymerization solvent. 
     
     
       26. The process according to claim 25, wherein said basic aqueous solution is selected from the group consisting of aqueous solutions of NaOH, KOH, Na 2  CO 3 , K 2  CO 3 , NaHCO 2 , Ca(OH) 2  and CaO. 
     
     
       27. The process according to claim 26, wherein the concentration of said basic aqueous solution is 0.1 to 20 wt %. 
     
     
       28. The process according to claim 25, wherein the amount of polymerization solvent in said mixed precipitation solution is less than 50% by weight of said total precipitating solution. 
     
     
       29. The process according to claim 1, wherein said aromatic polyamide is poly(p-phenylene terephthalamide).